Measures of Central Tendency: Definitions & Practice

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  • 0:01 What Is Central Tendency?
  • 0:53 Mode, Mean and Median
  • 2:53 Example
  • 4:30 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

After watching this video, you will be able to explain the meaning of the terms central tendency, mode, mean and median. You will also be able to calculate these three values from provided data. A short quiz will follow.

What Is Central Tendency?

A central tendency is a way of summarizing some data with a single number. In real life, the word 'average' is most commonly used.

For example, let's say you are measuring the heights of some flowers in your yard in centimeters, and your data reads 10, 15, 18, 19, 19, 19, 22, 24, 35, 40, 45. How do you summarize that data with a single number?

Well, there are lots of 19s, so maybe you just use the number 19. But the numbers go much higher above 19 than they go below. So there are lots of different ways to measure a central tendency, so maybe another method will be better. There are lots of different ways to measure a central tendency, and some of them are better than others in a particular situation.

Mode, Mean and Median

The three basic measures of central tendency you need to know about are mode, mean and median.

The mode is the number found most often. The way to remember this is that the first two letters are MO for mode, and that's also the same as the first two letters of most. MO for most. So in the data for the heights of flowers, 19 would be the mode.

The mean is what most people just call the average. You get the mean by adding up all the values and dividing by how many values there are. So for the flowers you would do 10 + 15 + 18 + 19 + 19 + 19 + 22 + 24 + 35 + 40 + 45, and divide the answer by 1-2-3-4-5-6-7-8-9-10-11. Divide by 11 because that's how many flowers you've measured, and you get a mean of 24.2.

Last of all is median, which is the number right in the middle of the list of data. The way to remember median is that it has the same number of letters as middle, and has a d: MiDdle, MeDian. For this, you count how many numbers there are (in this case, 11), and find the one right in the middle, which is the 6th number. That's the third 19. Before the third 19 there are five numbers, and after the third 19 there are five numbers. So the median is 19.

Note that if there are two numbers in the middle, the median is the number halfway between those two values.

Let's go over those again.

  • Mode is the most often; they both start with MO.
  • Median is the middle; they have the same number of letters.
  • And mean is the only one left, which is the average, where you add up all the values and divide by how many there are.

Example

One day, you decide to do an experiment to see how tall the average person in the grocery store is. You measure the height of fifteen people, and the results in inches are 58, 60, 61, 64, 65, 65, 66, 66, 66, 68, 69, 71, 73, 74, 78. These numbers have been put in numerical order. Sometimes you might be given the data in a random order and have to put it in numerical order yourself, so watch out for that.

What is the mode, mean and median of this data?

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